Productivity Maximization in Heavy Oil Wells
Personnel
| Chevron | TU PI's | Students |
|---|---|---|
| Brian Littlefield | Jagan Mahadevan | Joshua McCartt |
| Waisu Oladimeji |
Abstract
Effect of non-Newtonian Characteristics on Heavy Oil Reservoir Performance
Heavy oil has been found to exhibit non-Newtonian characteristics under certain reservoir conditions. In the previous study to this investigation it is shown by experimental measurements that heavy oils show pseudoplastic behavior under high pressure and temperature conditions. In this study, a numerical simulation model of non-Newtonian flow of heavy oil in reservoir is developed and validated. An unsteady state finite difference approach is used to construct the numerical solution to the flow problem of compressible heavy oil and gas through porous medium using power law model. In essence, the approach is that of a traditional black oil type of reservoir modeling with the non-Newtonian rheology included.
In its most general form, the model simulates a heavy oil flow in a horizontal reservoir. Flow behavior index and flow consistency index for saturated oil at high temperature and different pressures, obtained from experiments in a companion study were used in modeling heavy oil rheology. Modified Darcy’s law was used to model non-Newtonian flow of heavy oil through porous media. The simulator uses Cartesian coordinate grid systems. The resultant equations are highly non-linear in nature, analytical solution for which becomes almost impossible. Therefore fully implicit two dimensional finite difference scheme was used to solve these equations. Results of the numerical solution were validated with single phase non-Newtonian analytical solution available in literature. Moreover, close agreement was found in special cases, such as Newtonian flow in radial reservoir, for which analytical solution is available in literature.
The well inflow performance calculated using the simulator shows that as the exponent of the power law model (flow behavior index) decreases, the production flow rate decreases. Thus, in comparison to a Newtonian behavior, a power law behavior results in a poorer inflow performance. Consequently, production optimization could be achieved by controlling the fluid rheology and hence the power law parameters by maintaining solution gas in the oil phase. This may be achieved by operating the heavy oil wells above bubble point pressure. Hence there exists a potential to optimize well performance by appropriate bottom hole pressure control.